Approximately 15% of lung cancer in women occurs among non- smokers. A case-control epidemiologic study is proposed to investigate factors associated with the development of lung cancer in these non-smoking women. Risk factors of particular interest to the study include exposure to sidestream smoke at home, at the worksite and elsewhere, exposure to indoor radon in current and previous Florida homes, occupational exposures to lung carcinogens and a family history of lung cancer. The study will collect data over a four year period from 300 or more cases of histologically confirmed carcinoma of the lung and 600 age and race matched controls living in an eleven county study area. A structured interview will be utilized to collect data on the risk factors of interest and possible confounding factors. For all participants who have resided in Florida for ten years or longer, measurements will be made of indoor radon levels in current and prior Florida homes. Two alpha track detectors will be placed in each eligible and consenting household for a twelve month period. The result of this study will provide important new information on the etiology of lung cancer among non-smoking women.